This invention relates to cleaning dried, and/or aged paint, from surfaces where such paint is not desired. More particularly, this invention relates to cleaning paint from parts having one or more dried or cured layers of paint, to a novel water-based solution for accomplishing such cleaning, and to a concentrate from which the solution can be made by dilution with water only.
Current commercial practice in the art preponderantly utilizes solutions that comprise a component of amines and a component of organic solvent generally selected from the group consisting of simple alcohols and monoethers of glycols, most or all with molecules that contain no more than eight carbon atoms, in order to have sufficient water solubility. The amines used are typically alkanolamines like dimethyl ethanol amine, methyl isopropanol amine, and diethanol amine but are not limited to this class of amines. Typical solvents used in the solution are alcohols and glycol ethers, such as n-butanol, ethylene glycol mono butyl ether, diethylene glycol n-butyl ether, triethylene glycol methyl ether, propylene glycol normal butyl ether, dipropylene glycol methyl ether, propylene glycol methyl ether, and propylene glycol normal propyl ether. Typical concentrate formulas consist of 85 to 99% of solvent and 1 to 15% of alkanolamine, with the balance water. The concentrates are usually diluted to from 5% to 15%, by weight or volume, in deionized water for use as a working water-based paint-removing solution. Operating temperature when using the water-based solution is usually from 21 to 55.degree. C.
Although a large number of different types of compositions have been developed for the purpose of removing paint and other organic coatings from substrate surfaces, many of the paint stripper formulations in commercial use currently contain substantial quantities of relatively volatile organic solvents which are classified as “HAPS” (Hazardous Air Pollutants). In view of the recent increase in regulatory restrictions on the use of such substances, the development of coating removal compositions which are substantially or entirely HAPS-free is currently a subject of great interest. Unfortunately, however, many of the HAPS-free formulations developed to date are not as efficient in removing paint as the conventional solvent-based coating removal compositions. That is, the rate at which a coating is loosened from the substrate surface is often decreased significantly as the volatile organic solvent concentration is reduced. An object of the current invention is to provide a cleaner that is substantially or entirely HAPS-free which also provides adequate rates of coating removal even on completely dried and/or cured paint, and on aged paint. Other alternative and/or concurrent objects will become apparent from the description below.
Except in the claims and the operating examples, or where otherwise expressly indicated to the contrary, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word “about” in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred, however. Also, throughout the description and claims, unless expressly stated to the contrary: percent, “parts of”, and ratio values are by weight; the term “polymer” includes “oligomer”, “copolymer”, “terpolymer”, and the like; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description, and does not necessarily preclude chemical interactions among the constituents of a mixture once mixed; specification of materials in ionic form implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole, and any counterions thus implicitly specified preferably are selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, except for avoiding counterions that act adversely to the objects of the invention; the term “paint” and its grammatical variations includes any more specialized types of protective exterior coatings that are also known as, for example, lacquer, electropaint, shellac, top coat, base coat, color coat, and the like; and the term “mole” and its variations may be applied to ionic, chemically unstable neutral, or any other chemical species, whether actual or hypothetical, that is specified by the type(s) of atoms present and the number of each type of atom included in the unit defined, as well as to substances with well defined neutral molecules.